1. Field of the Invention
The present invention relates to a maleimide copolymer, a production method thereof, and a heat-resistant resin composition containing the copolymer.
2. Description of the Related Art
In order to improve the heat-resistance of conventional ABS resins etc., maleimide copolymers have been used as heat-resistance imparting materials (Patent Document 1 and Patent Document 2). However, due to the unpolymerized residual maleimide monomers, these maleimide copolymers have a yellow hue, causing the heat-resistant ABS resin compositions comprising the maleimide monomers to also take on a hue with a yellow tinge, so there were the problems of the color appearing unnatural and poor colorability.
In view of these problems, Patent Document 3 proposes a method of reducing residual maleimide monomers by adding liquid polybutadiene when producing a maleimide copolymer. Additionally, Patent Document 4 proposes a heat-resistance imparting material composed of a maleimide copolymer, an AS resin and a specific organic phosphorus compound.
Patent Document 1: JP-A S57-98536
Patent Document 2: JP-A S57-125241
Patent Document 3: JP-A2006-176578
Patent Document 4: JP-A 2003-41080